Doctor Who - U.N.I.T.

The Unified Intelligence Taskforce - formerly known as the United Nations Intelligence Taskforce, and more usually called UNIT - was a military organisation which operated under the auspices of the United Nations. Its remit was to investigate and combat paranormal and extraterrestrial threats to the Earth. UNIT was not the only alien defence organisation, but it was the one with which the Doctor had the closest personal involvement.

An early 20th century counterpart to UNIT was LONGBOW. This world security organisation was set up by the UN precursor, the League of Nations. LONGBOW dealt with the occasional extraterrestrial incident, but was disbanded after the League and it failed to prevent World War II.

The roots of UNIT itself, however, lay in later alien encounters. The Intrusion Countermeasures Group headed by Group Captain Ian Gilmore, which got involved in the Shoreditch Incident, served as a specialised military force with scientific assistance would seem almost a trial run for UNIT, though not an international organisation. Though Gilmore did have two scientific advisors serving much as the third incarnation of the Doctor and Dr. Elizabeth "Liz" Shaw would later, the seventh incarnation of the Doctor did most of the work on the technical end.

A second incident was the takeover of London by the Great Intelligence, with robot Yetis and a deadly cobweb-like fungus. Assisted by the Second Doctor, another group of British infantrymen, led by Colonel Alistair Gordon Lethbridge-Stewart of the Scots Guards beat back the Yeti from the tunnels of the London Underground.UNIT themselves would later consider this to be the origin of the organisation.

The United Nations were aware the world faced threats from extraterrestrial sources. Space programmes sent probes deeper and deeper into space; mankind was drawing attention to itself. Unable to get the British government to form a permanent special operations force for alien threats, Lethbridge-Stewart went over their heads to the UN Security Council, who proved more receptive. The UN established UNIT with the mandate to investigate, monitor and combat such threats. At the suggestion of Gilmore from the ICMG, Lethbridge-Stewart was promoted to the rank of Brigadier and put in charge of the British contingent. This contingent was organisationally known as Department C19 within the British government.
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One of UNIT's first missions was an intensive investigation of International Electromatics that turned violent. UNIT agents were killed and UNIT launched a helicopter raid to liberate prisoners at an Electromatics' facility. With the help, again, of the Second Doctor, UNIT discovered the company was a front for a Cybermen invasion and was able to defend against it. Lethbridge-Stewart became convinced of the necessity of scientific advice in battling extraterrestrial threats. He recruited Liz Shaw from the University of Cambridge. Coincidentally, the Third Doctor had been exiled to Earth by the Time Lords. He agreed to join UNIT as its scientific advisor just in time to help defeat the Autons. The Doctor continued to assist UNIT. Liz and he helped them fight such foes as The Silurians and the Primords. Liz Shaw left UNIT and was replaced by Jo Grant as the Doctor's assistant, though she only had managed to take science up to A level, of which she later said "I never said I passed". When he met her, UNIT made an enemy out of the Master. UNIT locked up the Master after several attempts to destroy Earth

When the Doctor's exile was ended, his association with UNIT became more sporadic, especially after his regeneration into his fourth incarnation. 

Ministry of Defence, UNIT headquarters

The Doctor did return to Earth with Sarah Jane Smith, but would work less with the Brigadier and more with such other officers as Colonel Faraday (the Brigadier having gone to Geneva) and Major Beresford. The Doctor, however, never officially left UNIT.

As a United Nations group, UNIT often served as security at peace conferences and the British contingent had foreign soldiers such as Sergeant Zbrigniev.

UNIT often faced hostility to its operations when investigating research facilities and companies. A common tactic against them was an appeal to any contacts in the Westminster government. These forced Lethbridge-Stewart either to back down or go over the government's heads to Geneva.

(Text from Tardis Data Core)

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